Deeply Virtual Compton Scattering Studies with CLAS and CLAS12

1. Deeply Virtual Compton Scattering Studies with CLAS and CLAS12 g Latifa Elouadrhiri Jefferson Lab CLAS t CLAS12

2. D. Mueller, X. Ji, A. Radyushkin,(1994-1997),… M. Burkardt, A. Belitsky (2000)… The size and structure of proton. Proton form factors, transversecharge and current distributions Nobel prize 1961- R. Hofstadter Internal constituents of the nucleon Quark longitudinal momentum and helicity distributions Nobel prize 1990 - J. Friedman, H. Kendall, R. Taylor GPDs connect the quark distribution in transverse space and longitudinal momentum Generalized PartonDistributions(GPDs)

3. Deeply Virtual Compton Scattering (DVCS) hard vertices g x – longitudinal quark momentum fraction x-x x+x 2x – longitudinal momentum transfer –t – Fourier conjugate to transverse impact parameter t Deeply Virtual Compton Scattering & GPDs GPDs depend on 3 variables, e.g.H(x, x, t).They describe the internal nucleon dynamics.

4. Form factors (sum rules) ] x [ 1 DIS at =t=0 å ò x = q dx H ( x , , t ) F1 ( t )Dirac f.f. q = q H ( x , 0 , 0 ) q ( x ) ] [ 1 å ò x = q dx E ( x , , t ) F2 ( t )Pauli f.f. ~ = D q ( x , 0 , 0 ) q ( x ) H q 1 1 ~ ~ ò ò x = x = q q dx H ( x , , t ) G ( t ) , dx E ( x , , t ) G ( t ) , , A q P q ~ ~ - - 1 1 x q q q q H , E , H , E ( x , , t ) 1 1 1 [ ] ò = - J G = x + x J q xdx H q( x , , 0 ) E q( x , , 0 ) 2 2 - 1 X. Ji, Phy.Rev.Lett.78,610(1997) Link to DIS and Elastic Form Factors Angular Momentum Sum Rule

5. Physical content of GPD E&H Nucleon matrix element of the Energy-Momentum Tensor of QCD contains 3 scalar form factor: M2(t) : Mass distribution inside the nucleon J (t) : Angular momentum distribution d1(t) : Forces and pressure distribution Directly measured in elastic graviton-proton scattering! GPDs are related to these form factors through 2nd moments

6. d4 ~ |TDVCS + TBH|2 dQ2dxBdtd AccessingGPDsThrough DVCS • GPDs are universal, they can be • determined in any suitable process Eo = 11 GeV Eo = 6 GeV Eo = 4 GeV BH DVCS BH TBH: given by elastic form factors TDVCS: determined by GPDs DVCS BH-DVCS interference generates beam and target asymmetries that carry the nucleon structure information.

7. GPDs & DVCS (at leading order:) Cross-sectionmeasurement and beam charge asymmetry (ReT) integrateGPDs over x Beam or target spin asymmetry containonlyImT, thereforeGPDsatx = x and -x

8. Ds 2s s+ - s- s+ + s- A = = x = xB/(2-xB) k = t/4M2 Accessing GPDsthrough polarization Polarized beam, unpolarized target: ~ H DsLU~ sinfIm{F1H+ x(F1+F2)H+kF2E}df Kinematically suppressed Unpolarized beam, longitudinal target: ~ ~ H DsUL~ sinfIm{F1H+x(F1+F2)(H+x/(1+x)E) -.. }df Kinematically suppressed Unpolarized beam, transverse target: H, E DsUT~ cosfIm{k(F2H– F1E) + …..}df Kinematicallysuppressed

9. CLAS 4.3 GeV HERMES 27 GeV 0 -180 +180 f(deg) First observation of DVCS/BH beam asymmetry e+pe+gX 2001 e-p e-pX Q2=2.5 GeV2 Q2=1.5 GeV2 Early GPD analysis of CLAS/HERMES/HERA data in LO/ NLO shows results consistent with handbag mechanism and lowest order pQCD. A. Freund (2003), A. Belitsky, et al. (2003) A(f) = asinf + bsin2f b/a << 1 twist-3 << twist-2

10. ~ H AUL is dominated by Hand fit model ~ model (H=0) ~ ~ H=0 H=0 First DVCS measurement with spin-aligned target Unpolarized beam, longitudinally spin-aligned target: ~ DsUL~ sinfIm{F1H+x(F1+F2)H+…}df S. Chen, et al., Phys. Rev. Lett 97, 072002 (2006) CLAS CLAS preliminary a = 0.252 ± 0.042 b = -0.022 ± 0.045 Consistent with leading twist

11. Hall A CLAS s.c. solenoid PbWO4 Electromagnetic calorimeter x, t, Q2 - dependence of Im(TDVCS) in wide kinematics. Constrain GPD models. First Dedicated DVCS Experiments at JLab Full reconstruction of all final state particles e, p, g High luminosity Azimuthal and Q2 dependence of Im(TDVCS) at fixed x. Test Bjorkenscaling.

12. Results of the Hall A DVCS experiment First absolute cross section measurements in the valence quark regime. Verify Bjorken scaling of cross section in limited Q2 range. Phys.Rev.Lett.97:262002,2006

13. Results of the CLAS E1-DVCS experiment Beam-spin asymmetries DsLU~ sinf{F1H+ x(F1+F2)H+kF2E}df Phys.Rev.Lett.100:162002,2008

14. GPD extraction from truncated expansion (H only) ~ Truncation allows analysis of x and t dependences of H, but neglecting H is problematic. H. Moutarde, Phys.Rev.D79:094021, 2009

15. Extractions of GPDs from full expansion A nearly model-independent GPD analysis in leading twist has become possible due the availability of beam-spin and target-spin asymmetry results at 3 values of t and fixed x. M. Guidal, Phys.Rev.Lett. B689:156-162,2010 • HIm drops with t similar to VGG model but has smaller magnitude • H-tilde tends to be larger than model prediction

16. CLAS12 - DVCS – Dedicated longitudinally polarized target experiment To extend GPD extraction from polarization data improvement of statistics and expansion of kinematical coverage is needed. Preliminary data from eg1-dvcs experiment have 10 times previous statistics AUL Pioneering results from data mining

17. CLAS12 - DVCS with transversely polarized target Transverse asymmetries AUT and ALT are sensitive to GPD E. GPDs E and H enter in the angular momentum sum rule. A precise measurement of AUT will help resolve the proton spin puzzle.

18. Add new hall CHL-2 Enhance equipment in existing halls JLab Upgrade to 12 GeV At 12 GeV, CEBAF is an ideal laboratory for GPD studies in the valence quark regime.

19. Hall B 12GeV upgrade overview from CLAS to CLAS12 Present Day CLAS CLAS will be replaced with CLAS12 CLAS12is designed to operate with order of magnitude higher luminosity. CLAS12designed to accommodate polarized solid state targets NH3, ND3 and HD.

20. H1, ZEUS Kinematic reach of the 12 GeV Upgrade Exclusive Processes H1, ZEUS 27 GeV 11 GeV 200 GeV JLab @ 12 GeV COMPASS HERMES Study of high xB domain requires high luminosity 0.7

21. ALU CLAS12 DVCS/BH- Beam Asymmetry at 12 GeV With large acceptance, measure large Q2, xB, t ranges simultaneously. A(Q2,xB,t) Ds(Q2,xB,t) s(Q2,xB,t)

22. Q2=5.5GeV2 xB = 0.35 -t = 0.25 GeV2 CLAS12- DVCS/BH- Beam Asymmetry Luminosity = 720fb-1

23. CLAS12 - DVCS/BH Beam Asymmetry epepg E = 11 GeV DsLU~sinfIm{F1H+..}df Selected Kinematics L = 1x1035 T = 2000 hrs ΔQ2= 1 GeV2 Δx= 0.05

24. CLAS12- DVCS/BH Longitudinal Target Asymmetry L = 2x1035 cm-2s-1 T = 1000 hrs DQ2 = 1GeV2 Dx = 0.05 epepg E = 11 GeV ~ Ds~sinfIm{F1H+x(F1+F2)H...}df

25. CLAS12- DVCS/BH Transverse Target Asymmetry Sample kinematics e p epg E = 11 GeV Q2=2.2 GeV2, xB = 0.25, -t = 0.5GeV2 Transverse polarized target Ds ~ cosfIm{k1(F2H– F1E) +…}df AUTx Target polarization in the scattering plane AUTy Target polarization perpendicular to the scattering plane Asymmetries highly sensitive to the u-quark contributions to the proton spin.

26. CLAS12– DVCS/BH beam spin asymmetry on neutrons This program requires adding a Central Neutron Detector (CDN) to the CLAS12 base equipment. DVCS on neutrons is sensitive to GPD En and the d-quark content of the nucleon spin. CND European Initiative led by: Orsay University

27. CLAS12 • Forward Detector: • - TORUS magnet • - Forward SVT tracker • HT Cherenkov Counter • Drift chamber system • LT Cherenkov Counter • Forward ToF System • Preshower calorimeter • E.M. calorimeter • Central Detector: • SOLENOID magnet • Barrel Silicon Tracker • Central Time-of-Flight • Polarized target (NSF) • Proposed upgrades: • Micromegas (CD) • Neutron detector (CD) • RICH detector (FD) • Forward Tagger (FD)

28. CLAS12 in construction - examples • Super Conducting Magnets • Conductor ready • Torus Coil case being prepared for coil winding • Silicon Vertex Tracker • Testing of the readout chip • Sensor testing • Forward Time of Flight • PMT testing at USC • Scintillator testing at USC

29. CLAS12 Under Construction - Examples • Drift Chambers • Wire stringing of RI at JLab • Wire stringing of RII at ODU • High Threshold Cerenkov • Mirror fabrication in the JLab Clean room • Mirror trimming at JLab Machine shop • Pre-Shower Calorimeter (MRI/NSF) • Module assembly • Fibers QA

30. 12 GeV Upgrade Project Schedule • Two short parasitic installation periods in FY10 • 6-month installation • May-Oct 2011 • 12-month installation • May 2012-May 2013 • Hall A commissioning start October 2013 • Hall D commissioning start • April 2014 • Halls B & C commissioning start October 2014 • Project Completion June 2015

31. CLAS CollaborationCollaboraiCollaboration Old Dominion University, Norfolk, VA Rensselaer Polytechnic Institute, Troy, NY Rice University, Houston, TX University of Richmond, Richmond, VA University of Rome Tor Vergata, Italy University of South Carolina, Columbia, SC Thomas Jefferson National Accelerator Facility, Newport News, VA Union College, Schenectady, NY University Santa Maria, Valparaiso, Chile Virginia Polytechnic Institute, Blacksburg, VA University of Virginia, Charlottesville, VA College of William and Mary, Williamsburg, VA Yerevan Institute of Physics, Yerevan, Armenia Brazil, Germany, Morocco and Ukraine, , have individuals or groups involved with CLAS, but with no formal collaboration at this stage. Arizona State University, Tempe, AZ University Bari, Bari, Italy University of California, Los Angeles, CA California State University, Dominguez Hills, CA Carnegie Mellon University, Pittsburgh, PA Catholic University of America CEA-Saclay, Gif-sur-Yvette, France Christopher Newport University, Newport News, VA University of Connecticut, Storrs, CT Edinburgh University, Edinburgh, UK University Ferrara, Ferrara, Italy Florida International University, Miami, FL Florida State University, Tallahassee, FL George Washington University, Washington, DC University of Glasgow, Glasgow, UK University of Grenoble, Grenoble, France Idaho State University, Pocatello, Idaho INFN, LaboratoriNazionalidiFrascati, Frascati, Italy INFN, SezionediGenova, Genova, Italy Institut de Physique Nucléaire, Orsay, France ITEP, Moscow, Russia James Madison University, Harrisonburg, VA Kyungpook University, Daegu, South Korea University of Massachusetts, Amherst, MA Moscow State University, Moscow, Russia University of New Hampshire, Durham, NH Norfolk State University, Norfolk, VA Ohio University, Athens, OH

32. Summary • The discovery of Generalized Parton Distributions • has opened up a new and exciting avenue of hadron • physics that needs exploration in dedicated experiments. • Moderate to high energy, high luminosity, and large acceptance spectrometers are needed to measure GPDs in deeply virtual exclusive processes. • The JLab 12 GeV Upgrade provides the tools to do this well and explore the nucleon at a much deeper level.

33. CLAS12- Institutions • Armenia: • - Yerevan Physics Institute, Yerevan, Armenia • United States of America: • Argonne National Laboratory, Argonne, Il • California State University, Dominguez Hills, CA • - Catholic University of America, Washington, DC • - College of William and Mary, Williamsburg, VA • - Christopher Newport University, Newport News, VA • - Fairfield University, Fairfield, CT • Florida International University, Miami, FL • Hampton University, Hampton, VA • - Idaho State University, Pocatella, ID • - James Madison University, Harrisionburg, VA • - Norfolk State University, Norfolk, VA • - Ohio University, Athens, OH • - Old Dominion University, Norfolk, VA • - Rensselaer Polytechnic Institute, Troy, NY • - Temple University, Philadelphia, PA • - Jefferson Lab, Newport News, VA • - University of Connecticut, Storrs, CT • - University of New Hampshire, Durham, NH • - University, of Richmond, Richmond, VA • - University of South Carolina, Columbia, SC • University of Virginia, Charlottesville, VA Chile: - University Santa Maria, Valparaiso France: - Grenoble University, IN2P3, Grenoble - Orsay University, IN2P3, Paris - CEA Saclay, IRFU, Paris • Italy: • - INFN - LNF, Roma • - INFN - Genova, Genova • INFN - University Bari, Bari • INFN - University Ferrara, Ferrara • - INFN - ISS, Roma • - INFN - Roma II, Tor Vergata, Roma Republic of Korea: - Kyungpook National University, Daegu, Korea Russian Federation: - MSU, Skobeltsin Institute for Nuclear Physics, Moscow - MSU, Institute for High Energy Physics, SiLab, Moscow - Institute for Theoretical and Experimental Physics, Moscow United Kingdom: - Edinburgh University, Edinburgh, Scotland - Glasgow University, Glasgow, Scotland 38 Institutions, November 2010